Radio frequency front end modules implementing coexisting time division duplexing and frequency division duplexing

ABSTRACT

Radio frequency front end modules implementing coexisting time division duplexing and frequency division duplexing are provided. In one aspect, a front end system includes a time-division duplexing transmit terminal, a time-division duplexing receive terminal, a frequency division duplexing terminal, and an antenna terminal. The front end system further includes first, second, and third switches configured to selectively connect the terminals to either a node or the antenna. The front end system also includes a controller configured to provide delays between disconnecting the terminals from the antenna and connecting the terminals to the node.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND Technological Field

Aspects of this disclosure relate to radio frequency (RF) communicationsystems, and in particular, front end modules for use in RFcommunication systems.

Description of the Related Technology

RF communication systems include a front end module which couples one ormore antennas to transmit and receive paths that communicate the RFsignals to/from a baseband system. Front end modules can be configuredto communicate using both time-division duplexing (TDD) and frequencydivision duplexing (FDD) communication. In implementing 5G, the frontend module may need to selectively connect a relatively large number ofbands to a limited number of antennas. Such front end modules may alsoimplement many carrier aggregation cases for the diversity receive path.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The systems, methods and devices of this disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

In one aspect, there is provided a front end system comprising: atime-division duplexing transmit terminal; a time-division duplexingreceive terminal; a frequency division duplexing terminal; an antennaterminal; a first switch configured to selectively connect thetime-division duplexing transmit terminal to either a first node or theantenna based on a first control signal; a second switch configured toselectively connect the time-division duplexing receive terminal toeither a second node or the antenna based on a second control signal; athird switch configured to connect the frequency division duplexingterminal to the antenna based on a third control signal; and acontroller configured to generate the first, second, and third controlsignals, the controller further configured to provide: i) a first delaybetween disconnecting the time-division duplexing transmit terminal fromthe antenna and connecting the time-division duplexing transmit terminalto the first node, and ii) a second delay between disconnecting thetime-division duplexing receiver terminal from the antenna andconnecting the time-division duplexing receive terminal to the secondnode.

The first node and the second node can be ground nodes.

The first switch can include a first serial sub-switch configured toselectively connect the time-division duplexing transmit terminal to theantenna and a first shunt sub-switch configured to selectively connectthe time-division duplexing transmit terminal to the first node, and thesecond switch can include a second serial sub-switch configured toselectively connect the time-division duplexing receive terminal to theantenna and a second shunt sub-switch configured to selectively connectthe time-division duplexing receive terminal to the second node.

The first control signal can include a first serial control signalconfigured to control the first serial sub-switch and a first shuntcontrol signal configured to control the first shunt sub-switch, and thesecond control signal can include a second serial control signalconfigured to control the second serial sub-switch and a second shuntcontrol signal configured to control the second shunt sub-switch.

The controller can be further configured to provide the first delaybetween transitioning the first serial control signal to an off valueand transitioning the first shunt control signal to an on value, and thecontroller can be further configured to provide the second delay betweentransitioning the second serial control signal to the off value andtransitioning the second shunt control signal to the on value.

The controller can be further configured to provide a third delaybetween transitioning the first shunt control signal to the off valueand transitioning the first serial control signal to the on value, andthe controller can be further configured to provide a fourth delaybetween transitioning the second shunt control signal to the off valueand transitioning the second serial control signal to the on value.

The controller can be further configured to adjust a length of the firstdelay and the second delay.

The controller can include both digital and analog circuitry configuredto implement the first delay and the second delay.

The controller can be further configured to switch between connectingthe time-division duplexing transmit terminal and the time-divisionduplexing receive terminal to the antenna while the frequency divisionduplexing terminal remains connected to the antenna.

In another aspect, there is provided a mobile device comprising: anantenna configured to transmit radio frequency signals to a basestation; a time-division duplexing power amplifier; a time-divisionduplexing low noise amplifier; a frequency division duplexing terminal;and a front end system coupled to the antenna, the time-divisionduplexing power amplifier, the time-division duplexing low noiseamplifier, and the frequency division duplexing terminal, the front endsystem including a first switch configured to selectively connect thetime-division duplexing power amplifier to either a first node or theantenna based on a first control signal, a second switch configured toselectively connect the time-division duplexing low noise amplifier toeither a second node or the antenna based on a second control signal, athird switch configured to connect the frequency division duplexingterminal to the antenna based on a third control signal, and acontroller configured to generate the first, second, and third controlsignals, the controller further configured to provide: i) a first delaybetween disconnecting the time-division duplexing power amplifier fromthe antenna and connecting the time-division duplexing power amplifierto the first node, and ii) a second delay between disconnecting thetime-division duplexing low noise amplifier from the antenna andconnecting the time-division duplexing low noise amplifier to the secondnode.

The first node and the second node can be ground nodes.

The first switch can include a first serial sub-switch configured toselectively connect the time-division duplexing power amplifier to theantenna and a first shunt sub-switch configured to selectively connectthe time-division duplexing power amplifier to the first node, and thesecond switch can include a second serial sub-switch configured toselectively connect the time-division duplexing low noise amplifier tothe antenna and a second shunt sub-switch configured to selectivelyconnect the time-division duplexing low noise amplifier to the secondnode.

The first control signal can include a first serial control signalconfigured to control the first serial sub-switch and a first shuntcontrol signal configured to control the first shunt sub-switch, and thesecond control signal can include a second serial control signalconfigured to control the second serial sub-switch and a second shuntcontrol signal configured to control the second shunt sub-switch.

The controller can be further configured to provide the first delaybetween transitioning the first serial control signal to an off valueand transitioning the first shunt control signal to an on value, and thecontroller can be further configured to provide the second delay betweentransitioning the second serial control signal to the off value andtransitioning the second shunt control signal to the on value.

The controller can be further configured to provide a third delaybetween transitioning the first shunt control signal to the off valueand transitioning the first serial control signal to the on value, andthe controller can be further configured to provide a fourth delaybetween transitioning the second shunt control signal to the off valueand transitioning the second serial control signal to the on value.

The controller can be further configured to adjust the length of thefirst delay and the second delay.

The controller can include both digital and analog circuitry configuredto implement the first delay and the second delay.

The controller can be further configured to switch between connectingthe time-division duplexing power amplifier and the time-divisionduplexing low noise amplifier to the antenna while the frequencydivision duplexing terminal remains connected to the antenna.

In yet another aspect, there is provided a method comprising: coupling,via a first switch, a time-division duplexing transmit terminal toeither a first node or an antenna based on a first control signal;coupling, via a second switch, a time-division duplexing receiveterminal to either a second node or the antenna based on a secondcontrol signal; coupling, via a third switch, a frequency divisionduplexing terminal to the antenna based on a third control signal;providing a first delay between disconnecting the time-divisionduplexing transmit terminal from the antenna and connecting thetime-division duplexing transmit terminal to the first node; andproviding a second delay between disconnecting the time-divisionduplexing receiver terminal from the antenna and connecting thetime-division duplexing receive terminal to the second node.

The method can further comprise adjusting a length of the first delayand the second delay.

The method can further comprise: selectively coupling, via a firstserial sub-switch, the time-division duplexing transmit terminal to theantenna; selectively coupling, via a first shunt sub-switch, thetime-division duplexing transmit terminal to the first node; selectivelycoupling, via a second serial sub-switch, the time-division duplexingreceive terminal to the antenna; and selectively coupling, a secondshunt sub-switch, the time-division duplexing receive terminal to thesecond node.

The method can further comprise: generating a first serial controlsignal to control the first serial sub-switch; generating a first shuntcontrol signal to control the first shunt sub-switch; generating asecond serial control signal to control the second serial sub-switch;and generating a second shunt control signal to control the second shuntsub-switch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of one example of a communicationnetwork.

FIG. 1B is a schematic diagram of one example of a mobile devicecommunicating via cellular and WiFi networks.

FIG. 2A is a schematic diagram of one example of a communication linkusing carrier aggregation.

FIG. 2B illustrates various examples of uplink carrier aggregation forthe communication link of FIG. 2A.

FIG. 2C illustrates various examples of downlink carrier aggregation forthe communication link of FIG. 2A.

FIG. 3 is a schematic diagram of one embodiment of a mobile device.

FIG. 4 is a schematic diagram of a power amplifier system according toone embodiment.

FIG. 5 is an example block diagram of a front end module in accordancewith aspects of this disclosure.

FIG. 6 is an example block diagram of a control system for the front endmodule of FIG. 5 in accordance with aspects of this disclosure.

FIG. 7 illustrates example control signals provided to the first andsecond switches.

FIG. 8 illustrates example control signals provided to the first andsecond switches including a delay in accordance with aspects of thisdisclosure.

FIG. 9 is a block diagram of an example programmable RC delay circuitwhich may be included as a part of the hybrid delay control block ofFIG. 6 in accordance with aspects of this disclosure.

DETAILED DESCRIPTION

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

The International Telecommunication Union (ITU) is a specialized agencyof the United Nations (UN) responsible for global issues concerninginformation and communication technologies, including the shared globaluse of radio spectrum.

The 3rd Generation Partnership Project (3GPP) is a collaboration betweengroups of telecommunications standard bodies across the world, such asthe Association of Radio Industries and Businesses (ARIB), theTelecommunications Technology Committee (TTC), the China CommunicationsStandards Association (CCSA), the Alliance for TelecommunicationsIndustry Solutions (ATIS), the Telecommunications Technology Association(TTA), the European Telecommunications Standards Institute (ETSI), andthe Telecommunications Standards Development Society, India (TSDSI).

Working within the scope of the ITU, 3GPP develops and maintainstechnical specifications for a variety of mobile communicationtechnologies, including, for example, second generation (2G) technology(for instance, Global System for Mobile Communications (GSM) andEnhanced Data Rates for GSM Evolution (EDGE)), third generation (3G)technology (for instance, Universal Mobile Telecommunications System(UMTS) and High Speed Packet Access (HSPA)), and fourth generation (4G)technology (for instance, Long Term Evolution (LTE) and LTE-Advanced).

The technical specifications controlled by 3GPP can be expanded andrevised by specification releases, which can span multiple years andspecify a breadth of new features and evolutions.

In one example, 3GPP introduced carrier aggregation (CA) for LTE inRelease 10. Although initially introduced with two downlink carriers,3GPP expanded carrier aggregation in Release 14 to include up to fivedownlink carriers and up to three uplink carriers. Other examples of newfeatures and evolutions provided by 3GPP releases include, but are notlimited to, License Assisted Access (LAA), enhanced LAA (eLAA),Narrowband Internet of things (NB-IOT), Vehicle-to-Everything (V2X), andHigh Power User Equipment (HPUE).

3GPP introduced Phase 1 of fifth generation (5G) technology in Release15, and introduced Phase 2 of 5G technology in Release 16 in 2020.Subsequent 3GPP releases will further evolve and expand 5G technology.5G technology is also referred to herein as 5G New Radio (NR).

5G NR supports or plans to support a variety of features, such ascommunications over millimeter wave spectrum, beamforming capability,high spectral efficiency waveforms, low latency communications, multipleradio numerology, and/or non-orthogonal multiple access (NOMA). Althoughsuch RF functionalities offer flexibility to networks and enhance userdata rates, supporting such features can pose a number of technicalchallenges.

The teachings herein are applicable to a wide variety of communicationsystems, including, but not limited to, communication systems usingadvanced cellular technologies, such as LTE-Advanced, LTE-Advanced Pro,and/or 5G NR.

FIG. 1A is a schematic diagram of one example of a communication network10. The communication network 10 includes a macro cell base station 1, asmall cell base station 3, and various examples of user equipment (UE),including a first mobile device 2 a, a wireless-connected car 2 b, alaptop 2 c, a stationary wireless device 2 d, a wireless-connected train2 e, a second mobile device 2 f, and a third mobile device 2 g.

Although specific examples of base stations and user equipment areillustrated in FIG. 1A, a communication network can include basestations and user equipment of a wide variety of types and/or numbers.

For instance, in the example shown, the communication network 10includes the macro cell base station 1 and the small cell base station3. The small cell base station 3 can operate with relatively lowerpower, shorter range, and/or with fewer concurrent users relative to themacro cell base station 1. The small cell base station 3 can also bereferred to as a femtocell, a picocell, or a microcell. Although thecommunication network 10 is illustrated as including two base stations,the communication network 10 can be implemented to include more or fewerbase stations and/or base stations of other types.

Although various examples of user equipment are shown, the teachingsherein are applicable to a wide variety of user equipment, including,but not limited to, mobile phones, tablets, laptops, IoT devices,wearable electronics, customer premises equipment (CPE),wireless-connected vehicles, wireless relays, and/or a wide variety ofother communication devices. Furthermore, user equipment includes notonly currently available communication devices that operate in acellular network, but also subsequently developed communication devicesthat will be readily implementable with the inventive systems,processes, methods, and devices as described and claimed herein.

The illustrated communication network 10 of FIG. 1A supportscommunications using a variety of cellular technologies, including, forexample, 4G LTE and 5G NR. In certain implementations, the communicationnetwork 10 is further adapted to provide a wireless local area network(WLAN), such as WiFi. Although various examples of communicationtechnologies have been provided, the communication network 10 can beadapted to support a wide variety of communication technologies.

Various communication links of the communication network 10 have beendepicted in FIG. 1A. The communication links can be duplexed in a widevariety of ways, including, for example, using frequency-divisionduplexing (FDD) and/or time-division duplexing (TDD). FDD is a type ofradio frequency communications that uses different frequencies fortransmitting and receiving signals. FDD can provide a number ofadvantages, such as high data rates and low latency. In contrast, TDD isa type of radio frequency communications that uses about the samefrequency for transmitting and receiving signals, and in which transmitand receive communications are switched in time. TDD can provide anumber of advantages, such as efficient use of spectrum and variableallocation of throughput between transmit and receive directions.

In certain implementations, user equipment can communicate with a basestation using one or more of 4G LTE, 5G NR, and WiFi technologies. Incertain implementations, enhanced license assisted access (eLAA) is usedto aggregate one or more licensed frequency carriers (for instance,licensed 4G LTE and/or 5G NR frequencies), with one or more unlicensedcarriers (for instance, unlicensed WiFi frequencies).

As shown in FIG. 1A, the communication links include not onlycommunication links between UE and base stations, but also UE to UEcommunications and base station to base station communications. Forexample, the communication network 10 can be implemented to supportself-fronthaul and/or self-backhaul (for instance, as between mobiledevice 2 g and mobile device 2 f).

The communication links can operate over a wide variety of frequencies.In certain implementations, communications are supported using 5G NRtechnology over one or more frequency bands that are less than 6Gigahertz (GHz) and/or over one or more frequency bands that are greaterthan 6 GHz. For example, the communication links can serve FrequencyRange 1 (FR1), Frequency Range 2 (FR2), or a combination thereof. In oneembodiment, one or more of the mobile devices support a HPUE power classspecification.

In certain implementations, a base station and/or user equipmentcommunicates using beamforming. For example, beamforming can be used tofocus signal strength to overcome path losses, such as high lossassociated with communicating over high signal frequencies. In certainembodiments, user equipment, such as one or more mobile phones,communicate using beamforming on millimeter wave frequency bands in therange of 30 GHz to 300 GHz and/or upper centimeter wave frequencies inthe range of 6 GHz to 30 GHz, or more particularly, 24 GHz to 30 GHz.

Different users of the communication network 10 can share availablenetwork resources, such as available frequency spectrum, in a widevariety of ways.

In one example, frequency division multiple access (FDMA) is used todivide a frequency band into multiple frequency carriers. Additionally,one or more carriers are allocated to a particular user. Examples ofFDMA include, but are not limited to, single carrier FDMA (SC-FDMA) andorthogonal FDMA (OFDMA). OFDMA is a multicarrier technology thatsubdivides the available bandwidth into multiple mutually orthogonalnarrowband subcarriers, which can be separately assigned to differentusers.

Other examples of shared access include, but are not limited to, timedivision multiple access (TDMA) in which a user is allocated particulartime slots for using a frequency resource, code division multiple access(CDMA) in which a frequency resource is shared amongst different usersby assigning each user a unique code, space-divisional multiple access(SDMA) in which beamforming is used to provide shared access by spatialdivision, and non-orthogonal multiple access (NOMA) in which the powerdomain is used for multiple access. For example, NOMA can be used toserve multiple users at the same frequency, time, and/or code, but withdifferent power levels.

Enhanced mobile broadband (eMBB) refers to technology for growing systemcapacity of LTE networks. For example, eMBB can refer to communicationswith a peak data rate of at least 10 Gbps and a minimum of 100 Mbps foreach user. Ultra-reliable low latency communications (uRLLC) refers totechnology for communication with very low latency, for instance, lessthan 2 milliseconds. uRLLC can be used for mission-criticalcommunications such as for autonomous driving and/or remote surgeryapplications. Massive machine-type communications (mMTC) refers to lowcost and low data rate communications associated with wirelessconnections to everyday objects, such as those associated with Internetof Things (IoT) applications.

The communication network 10 of FIG. 1A can be used to support a widevariety of advanced communication features, including, but not limitedto, eMBB, uRLLC, and/or mMTC.

FIG. 1B is a schematic diagram of one example of a mobile device 2 acommunicating via cellular and WiFi networks. For example, as shown inFIG. 1B, the mobile device 2 a communicates with a base station 1 of acellular network and with a WiFi access point 3 of a WiFi network. FIG.1B also depicts examples of other user equipment (UE) communicating withthe base station 1, for instance, a wireless-connected car 2 b andanother mobile device 2 c. Furthermore, FIG. 1B also depicts examples ofother WiFi-enabled devices communicating with the WiFi access point 3,for instance, a laptop 4.

Although specific examples of cellular UE and WiFi-enabled devices isshown, a wide variety of types of devices can communicate using cellularand/or WiFi networks. Examples of such devices, include, but are notlimited to, mobile phones, tablets, laptops, Internet of Things (IoT)devices, wearable electronics, customer premises equipment (CPE),wireless-connected vehicles, wireless relays, and/or a wide variety ofother communication devices.

In certain implementations, UE, such as the mobile device 2 a of FIG.1B, is implemented to support communications using a number oftechnologies, including, but not limited to, 2G, 3G, 4G (including LTE,LTE-Advanced, and LTE-Advanced Pro), 5G NR, WLAN (for instance, WiFi),WPAN (for instance, Bluetooth and ZigBee), WMAN (for instance, WiMax),and/or GPS. In certain implementations, enhanced license assisted access(eLAA) is used to aggregate one or more licensed frequency carriers (forinstance, licensed 4G LTE and/or 5G NR frequencies), with one or moreunlicensed carriers (for instance, unlicensed WiFi frequencies).

Furthermore, certain UE can communicate not only with base stations andaccess points, but also with other UE. For example, thewireless-connected car 2 b can communicate with a wireless-connectedpedestrian 2 d, a wireless-connected stop light 2 e, and/or anotherwireless-connected car 2 f using vehicle-to-vehicle (V2V) and/orvehicle-to-everything (V2X) communications.

Although various examples of communication technologies have beendescribed, mobile devices can be implemented to support a wide range ofcommunications.

Various communication links have been depicted in FIG. 1B. Thecommunication links can be duplexed in a wide variety of ways,including, for example, using frequency-division duplexing (FDD) and/ortime-division duplexing (TDD). FDD is a type of radio frequencycommunications that uses different frequencies for transmitting andreceiving signals. FDD can provide a number of advantages, such as highdata rates and low latency. In contrast, TDD is a type of radiofrequency communications that uses about the same frequency fortransmitting and receiving signals, and in which transmit and receivecommunications are switched in time. TDD can provide a number ofadvantages, such as efficient use of spectrum and variable allocation ofthroughput between transmit and receive directions.

Different users of the illustrated communication networks can shareavailable network resources, such as available frequency spectrum, in awide variety of ways. In one example, frequency division multiple access(FDMA) is used to divide a frequency band into multiple frequencycarriers. Additionally, one or more carriers are allocated to aparticular user. Examples of FDMA include, but are not limited to,single carrier FDMA (SC-FDMA) and orthogonal FDMA (OFDMA). OFDM is amulticarrier technology that subdivides the available bandwidth intomultiple mutually orthogonal narrowband subcarriers, which can beseparately assigned to different users.

Other examples of shared access include, but are not limited to, timedivision multiple access (TDMA) in which a user is allocated particulartime slots for using a frequency resource, code division multiple access(CDMA) in which a frequency resource is shared amongst different usersby assigning each user a unique code, space-divisional multiple access(SDMA) in which beamforming is used to provide shared access by spatialdivision, and non-orthogonal multiple access (NOMA) in which the powerdomain is used for multiple access. For example, NOMA can be used toserve multiple users at the same frequency, time, and/or code, but withdifferent power levels.

Certain RF communication systems include multiple transceivers forcommunicating using different wireless networks, over multiple frequencybands, and/or using different communication standards. Althoughimplementing an RF communication system in this manner can expandfunctionality, increase bandwidth, and/or enhance flexibility, a numberof coexistence issues can arise between the transceivers operatingwithin the RF communication system.

For example, an RF communication system can include a cellulartransceiver for processing RF signals communicated over a cellularnetwork and a wireless local area network (WLAN) transceiver forprocessing RF signals communicated over a WLAN network, such as a WiFinetwork. For instance, the mobile device 2 a of FIG. 1B is operable tocommunicate using cellular and WiFi networks.

Although implementing the RF communication system in this manner canprovide a number of benefits, a mutual desensitization effect can arisefrom cellular transmissions interfering with reception of WiFi signalsand/or from WiFi transmissions interfering with reception of cellularsignals.

In one example, cellular Band 7 can give rise to mutual desensitizationwith respect to 2.4 Gigahertz (GHz) WiFi. For instance, Band 7 has anFDD duplex and operates over a frequency range of about 2.62 GHz to 2.69GHz for downlink and over a frequency range of about 2.50 GHz to about2.57 GHz for uplink, while 2.4 GHz WiFi has TDD duplex and operates overa frequency range of about 2.40 GHz to about 2.50 GHz. Thus, cellularBand 7 and 2.4 GHz WiFi are adjacent in frequency, and RF signal leakagedue to the high power transmitter of one transceiver/front end affectsreceiver performance of the other transceiver/front end, particularly atborder frequency channels.

In another example, cellular Band 40 and 2.4 GHz WiFi can give rise tomutual desensitization. For example, Band 40 has a TDD duplex andoperates over a frequency range of about 2.30 GHz to about 2.40 GHz,while 2.4 GHz WiFi has TDD duplex and operates over a frequency range ofabout 2.40 GHz to about 2.50 GHz. Accordingly, cellular Band 40 and 2.4GHz WiFi are adjacent in frequency and give rise to a number ofcoexistence issues, particularly at border frequency channels.

Desensitization can arise not only from direct leakage of an aggressortransmit signal to a victim receiver, but also from spectral regrowthcomponents generated in the transmitter. Such interference can lierelatively closely in frequency with the victim receive signal and/ordirectly overlap it.

FIG. 2A is a schematic diagram of one example of a communication linkusing carrier aggregation. Carrier aggregation can be used to widenbandwidth of the communication link by supporting communications overmultiple frequency carriers, thereby increasing user data rates andenhancing network capacity by utilizing fragmented spectrum allocations.

In the illustrated example, the communication link is provided between abase station 21 and a mobile device 22. As shown in FIG. 2A, thecommunications link includes a downlink channel used for RFcommunications from the base station 21 to the mobile device 22, and anuplink channel used for RF communications from the mobile device 22 tothe base station 21.

Although FIG. 2A illustrates carrier aggregation in the context of FDDcommunications, carrier aggregation can also be used for TDDcommunications.

In certain implementations, a communication link can provideasymmetrical data rates for a downlink channel and an uplink channel.For example, a communication link can be used to support a relativelyhigh downlink data rate to enable high speed streaming of multimediacontent to a mobile device, while providing a relatively slower datarate for uploading data from the mobile device to the cloud.

In the illustrated example, the base station 21 and the mobile device 22communicate via carrier aggregation, which can be used to selectivelyincrease bandwidth of the communication link. Carrier aggregationincludes contiguous aggregation, in which contiguous carriers within thesame operating frequency band are aggregated. Carrier aggregation canalso be non-contiguous, and can include carriers separated in frequencywithin a common band or in different bands.

In the example shown in FIG. 2A, the uplink channel includes threeaggregated component carriers f_(UL1), f_(UL2), and f_(UL3).Additionally, the downlink channel includes five aggregated componentcarriers f_(DL1), f_(DL2), f_(DL3), f_(DL4), and f_(DL5). Although oneexample of component carrier aggregation is shown, more or fewercarriers can be aggregated for uplink and/or downlink. Moreover, anumber of aggregated carriers can be varied over time to achieve desireduplink and downlink data rates.

For example, a number of aggregated carriers for uplink and/or downlinkcommunications with respect to a particular mobile device can changeover time. For example, the number of aggregated carriers can change asthe device moves through the communication network and/or as networkusage changes over time.

FIG. 2B illustrates various examples of uplink carrier aggregation forthe communication link of FIG. 2A. FIG. 2B includes a first carrieraggregation scenario 31, a second carrier aggregation scenario 32, and athird carrier aggregation scenario 33, which schematically depict threetypes of carrier aggregation.

The carrier aggregation scenarios 31-33 illustrate different spectrumallocations for a first component carrier f_(UL1), a second componentcarrier f_(UL2), and a third component carrier f_(UL3). Although FIG. 2Bis illustrated in the context of aggregating three component carriers,carrier aggregation can be used to aggregate more or fewer carriers.Moreover, although illustrated in the context of uplink, the aggregationscenarios are also applicable to downlink.

The first carrier aggregation scenario 31 illustrates intra-bandcontiguous carrier aggregation, in which component carriers that areadjacent in frequency and in a common frequency band are aggregated. Forexample, the first carrier aggregation scenario 31 depicts aggregationof component carriers f_(UL1), f^(UL2), and f_(UL3) that are contiguousand located within a first frequency band BAND1.

With continuing reference to FIG. 2B, the second carrier aggregationscenario 32 illustrates intra-band non-continuous carrier aggregation,in which two or more components carriers that are non-adjacent infrequency and within a common frequency band are aggregated. Forexample, the second carrier aggregation scenario 32 depicts aggregationof component carriers f_(UL1), f_(UL2), and f_(UL3) that arenon-contiguous, but located within a first frequency band BAND1.

The third carrier aggregation scenario 33 illustrates inter-bandnon-contiguous carrier aggregation, in which component carriers that arenon-adjacent in frequency and in multiple frequency bands areaggregated. For example, the third carrier aggregation scenario 33depicts aggregation of component carriers f_(UL1) and f_(UL2) of a firstfrequency band BAND1 with component carrier f_(UL3) of a secondfrequency band BAND2.

FIG. 2C illustrates various examples of downlink carrier aggregation forthe communication link of FIG. 2A. The examples depict various carrieraggregation scenarios 34-38 for different spectrum allocations of afirst component carrier f_(DL1), a second component carrier f_(DL2), athird component carrier f_(DL3), a fourth component carrier f_(DL4), anda fifth component carrier f_(DL5). Although FIG. 2C is illustrated inthe context of aggregating five component carriers, carrier aggregationcan be used to aggregate more or fewer carriers. Moreover, althoughillustrated in the context of downlink, the aggregation scenarios arealso applicable to uplink.

The first carrier aggregation scenario 34 depicts aggregation ofcomponent carriers that are contiguous and located within the samefrequency band. Additionally, the second carrier aggregation scenario 35and the third carrier aggregation scenario 36 illustrates two examplesof aggregation that are non-contiguous, but located within the samefrequency band. Furthermore, the fourth carrier aggregation scenario 37and the fifth carrier aggregation scenario 38 illustrates two examplesof aggregation in which component carriers that are non-adjacent infrequency and in multiple frequency bands are aggregated. As a number ofaggregated component carriers increases, a complexity of possiblecarrier aggregation scenarios also increases.

With reference to FIGS. 2A-2C, the individual component carriers used incarrier aggregation can be of a variety of frequencies, including, forexample, frequency carriers in the same band or in multiple bands.Additionally, carrier aggregation is applicable to implementations inwhich the individual component carriers are of about the same bandwidthas well as to implementations in which the individual component carriershave different bandwidths.

Certain communication networks allocate a particular user device with aprimary component carrier (PCC) or anchor carrier for uplink and a PCCfor downlink. Additionally, when the mobile device communicates using asingle frequency carrier for uplink or downlink, the user devicecommunicates using the PCC. To enhance bandwidth for uplinkcommunications, the uplink PCC can be aggregated with one or more uplinksecondary component carriers (SCCs). Additionally, to enhance bandwidthfor downlink communications, the downlink PCC can be aggregated with oneor more downlink SCCs.

In certain implementations, a communication network provides a networkcell for each component carrier. Additionally, a primary cell canoperate using a PCC, while a secondary cell can operate using a SCC. Theprimary and secondary cells may have different coverage areas, forinstance, due to differences in frequencies of carriers and/or networkenvironment.

License assisted access (LAA) refers to downlink carrier aggregation inwhich a licensed frequency carrier associated with a mobile operator isaggregated with a frequency carrier in unlicensed spectrum, such asWiFi. LAA employs a downlink PCC in the licensed spectrum that carriescontrol and signaling information associated with the communicationlink, while unlicensed spectrum is aggregated for wider downlinkbandwidth when available. LAA can operate with dynamic adjustment ofsecondary carriers to avoid WiFi users and/or to coexist with WiFiusers. Enhanced license assisted access (eLAA) refers to an evolution ofLAA that aggregates licensed and unlicensed spectrum for both downlinkand uplink.

FIG. 3 is a schematic diagram of one embodiment of a mobile device 800.The mobile device 800 includes a baseband system 801, a transceiver 802,a front end system 803, antennas 804, a power management system 805, amemory 806, a user interface 807, and a battery 808.

The mobile device 800 can be used communicate using a wide variety ofcommunications technologies, including, but not limited to, 2G, 3G, 4G(including LTE, LTE-Advanced, and LTE-Advanced Pro), 5G NR, WLAN (forinstance, WiFi), WPAN (for instance, Bluetooth and ZigBee), WMAN (forinstance, WiMax), and/or GPS technologies.

The transceiver 802 generates RF signals for transmission and processesincoming RF signals received from the antennas 804. It will beunderstood that various functionalities associated with the transmissionand receiving of RF signals can be achieved by one or more componentsthat are collectively represented in FIG. 3 as the transceiver 802. Inone example, separate components (for instance, separate circuits ordies) can be provided for handling certain types of RF signals.

The front end system 803 aids in conditioning signals transmitted toand/or received from the antennas 804. In the illustrated embodiment,the front end system 803 includes antenna tuning circuitry 810, poweramplifiers (PAs) 811, low noise amplifiers (LNAs) 812, filters 813,switches 814, and signal splitting/combining circuitry 815. However,other implementations are possible.

For example, the front end system 803 can provide a number offunctionalities, including, but not limited to, amplifying signals fortransmission, amplifying received signals, filtering signals, switchingbetween different bands, switching between different power modes,switching between transmission and receiving modes, duplexing ofsignals, multiplexing of signals (for instance, diplexing ortriplexing), or some combination thereof.

In certain implementations, the mobile device 800 supports carrieraggregation, thereby providing flexibility to increase peak data rates.Carrier aggregation can be used for both Frequency Division Duplexing(FDD) and Time Division Duplexing (TDD), and may be used to aggregate aplurality of carriers or channels. Carrier aggregation includescontiguous aggregation, in which contiguous carriers within the sameoperating frequency band are aggregated. Carrier aggregation can also benon-contiguous, and can include carriers separated in frequency within acommon band or in different bands.

The antennas 804 can include antennas used for a wide variety of typesof communications. For example, the antennas 804 can include antennasfor transmitting and/or receiving signals associated with a wide varietyof frequencies and communications standards.

In certain implementations, the antennas 804 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The mobile device 800 can operate with beamforming in certainimplementations. For example, the front end system 803 can includeamplifiers having controllable gain and phase shifters havingcontrollable phase to provide beam formation and directivity fortransmission and/or reception of signals using the antennas 804. Forexample, in the context of signal transmission, the amplitude and phasesof the transmit signals provided to the antennas 804 are controlled suchthat radiated signals from the antennas 804 combine using constructiveand destructive interference to generate an aggregate transmit signalexhibiting beam-like qualities with more signal strength propagating ina given direction. In the context of signal reception, the amplitude andphases are controlled such that more signal energy is received when thesignal is arriving to the antennas 804 from a particular direction. Incertain implementations, the antennas 804 include one or more arrays ofantenna elements to enhance beamforming.

The baseband system 801 is coupled to the user interface 807 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 801 provides the transceiver 802with digital representations of transmit signals, which the transceiver802 processes to generate RF signals for transmission. The basebandsystem 801 also processes digital representations of received signalsprovided by the transceiver 802. As shown in FIG. 3, the baseband system801 is coupled to the memory 806 of facilitate operation of the mobiledevice 800.

The memory 806 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of themobile device 800 and/or to provide storage of user information.

The power management system 805 provides a number of power managementfunctions of the mobile device 800. In certain implementations, thepower management system 805 includes a PA supply control circuit thatcontrols the supply voltages of the power amplifiers 811. For example,the power management system 805 can be configured to change the supplyvoltage(s) provided to one or more of the power amplifiers 811 toimprove efficiency, such as power added efficiency (PAE).

As shown in FIG. 3, the power management system 805 receives a batteryvoltage from the battery 808. The battery 808 can be any suitablebattery for use in the mobile device 800, including, for example, alithium-ion battery.

FIG. 4 is a schematic diagram of a power amplifier system 860 accordingto one embodiment. The illustrated power amplifier system 860 includes abaseband processor 841, a transmitter/observation receiver 842, a poweramplifier (PA) 843, a directional coupler 844, front-end circuitry 845,an antenna 846, a PA bias control circuit 847, and a PA supply controlcircuit 848. The illustrated transmitter/observation receiver 842includes an I/Q modulator 857, a mixer 858, and an analog-to-digitalconverter (ADC) 859. In certain implementations, thetransmitter/observation receiver 842 is incorporated into a transceiver.

The baseband processor 841 can be used to generate an in-phase (I)signal and a quadrature-phase (Q) signal, which can be used to representa sinusoidal wave or signal of a desired amplitude, frequency, andphase. For example, the I signal can be used to represent an in-phasecomponent of the sinusoidal wave and the Q signal can be used torepresent a quadrature-phase component of the sinusoidal wave, which canbe an equivalent representation of the sinusoidal wave. In certainimplementations, the I and Q signals can be provided to the I/Qmodulator 857 in a digital format. The baseband processor 841 can be anysuitable processor configured to process a baseband signal. Forinstance, the baseband processor 841 can include a digital signalprocessor, a microprocessor, a programmable core, or any combinationthereof. Moreover, in some implementations, two or more basebandprocessors 841 can be included in the power amplifier system 860.

The I/Q modulator 857 can be configured to receive the I and Q signalsfrom the baseband processor 841 and to process the I and Q signals togenerate an RF signal. For example, the I/Q modulator 857 can includedigital-to-analog converters (DACs) configured to convert the I and Qsignals into an analog format, mixers for upconverting the I and Qsignals to RF, and a signal combiner for combining the upconverted I andQ signals into an RF signal suitable for amplification by the poweramplifier 843. In certain implementations, the I/Q modulator 857 caninclude one or more filters configured to filter frequency content ofsignals processed therein.

The power amplifier 843 can receive the RF signal from the I/Q modulator857, and when enabled can provide an amplified RF signal to the antenna846 via the front-end circuitry 845.

The front-end circuitry 845 can be implemented in a wide variety ofways. In one example, the front-end circuitry 845 includes one or moreswitches, filters, diplexers, multiplexers, and/or other components. Inanother example, the front-end circuitry 845 is omitted in favor of thepower amplifier 843 providing the amplified RF signal directly to theantenna 846.

The directional coupler 844 senses an output signal of the poweramplifier 823. Additionally, the sensed output signal from thedirectional coupler 844 is provided to the mixer 858, which multipliesthe sensed output signal by a reference signal of a controlledfrequency. The mixer 858 operates to generate a downshifted signal bydownshifting the sensed output signal's frequency content. Thedownshifted signal can be provided to the ADC 859, which can convert thedownshifted signal to a digital format suitable for processing by thebaseband processor 841. Including a feedback path from the output of thepower amplifier 843 to the baseband processor 841 can provide a numberof advantages. For example, implementing the baseband processor 841 inthis manner can aid in providing power control, compensating fortransmitter impairments, and/or in performing digital pre-distortion(DPD). Although one example of a sensing path for a power amplifier isshown, other implementations are possible.

The PA supply control circuit 848 receives a power control signal fromthe baseband processor 841, and controls supply voltages of the poweramplifier 843. In the illustrated configuration, the PA supply controlcircuit 848 generates a first supply voltage V_(CC1) for powering aninput stage of the power amplifier 843 and a second supply voltageV_(CC2) for powering an output stage of the power amplifier 843. The PAsupply control circuit 848 can control the voltage level of the firstsupply voltage V_(CC1) and/or the second supply voltage V_(CC2) toenhance the power amplifier system's PAE.

The PA supply control circuit 848 can employ various power managementtechniques to change the voltage level of one or more of the supplyvoltages over time to improve the power amplifier's power addedefficiency (PAE), thereby reducing power dissipation.

One technique for improving efficiency of a power amplifier is averagepower tracking (APT), in which a DC-to-DC converter is used to generatea supply voltage for a power amplifier based on the power amplifier'saverage output power. Another technique for improving efficiency of apower amplifier is envelope tracking (ET), in which a supply voltage ofthe power amplifier is controlled in relation to the envelope of the RFsignal. Thus, when a voltage level of the envelope of the RF signalincreases the voltage level of the power amplifier's supply voltage canbe increased. Likewise, when the voltage level of the envelope of the RFsignal decreases the voltage level of the power amplifier's supplyvoltage can be decreased to reduce power consumption.

In certain configurations, the PA supply control circuit 848 is amulti-mode supply control circuit that can operate in multiple supplycontrol modes including an APT mode and an ET mode. For example, thepower control signal from the baseband processor 841 can instruct the PAsupply control circuit 848 to operate in a particular supply controlmode.

As shown in FIG. 4, the PA bias control circuit 847 receives a biascontrol signal from the baseband processor 841, and generates biascontrol signals for the power amplifier 843. In the illustratedconfiguration, the bias control circuit 847 generates bias controlsignals for both an input stage of the power amplifier 843 and an outputstage of the power amplifier 843. However, other implementations arepossible.

Embodiments of RF Front End Modules

As described above, communications systems typically include an RF frontend designed to connect a one or more band paths to one or more antennasand process the RF signals communicated therebetween. It may bedesirable to implement carrier aggregation over an increasingly greaternumber of bands of a 5G system. Since an RF communication systemstypically have a limited number of antennas, as more bands are includedin the carrier agreement implementation of the front end modules of 5Gsystems, it may be necessary both a TDD band switch and an FDD bandswitch share the same antenna port of an antenna switch block.

FIG. 5 is an example block diagram of a front end module 100 inaccordance with aspects of this disclosure. As shown in FIG. 5, thefront end module 100 includes a TDD transmit band terminal 102, a TDDreceive band terminal 106, an FDD band terminal 110, and an antenna 124.The antenna is connected to each of the terminals 102-110 via a switch122. The TDD transmit band terminal 102 may be connected to a poweramplifier (e.g., the power amplifier 843 of FIG. 4) configured toamplify an RF signal for transmission via the antenna. The TDD receiveband terminal 106 may be connected to a low noise amplifier (e.g., thelow noise amplifier 812) configured to amplify an RF signal received viathe antenna. The FDD band terminal 110 may be connected to both a poweramplifier and a low noise amplifier, configured to operate on differentfrequencies.

Three paths are formed between the band terminals 102-110 and theantenna: path A is formed between the TDD transmit band terminal 102 andthe antenna 124, path B is formed between the TDD receive band terminal106 and the antenna 124, and path C is formed between the FDD bandterminal 110 and the antenna 124. Each of the paths may include acorresponding filter 116 configured to pass frequencies corresponding tothe bands of the band terminals 102-110 and reject other frequencies.

In order to implement carrier aggregation on both the TDD band and theFDD band, the switch 122 may be configured to connect both the FDD bandterminal 110 and one of the TDD transmit band terminal 102 and the TDDreceive band terminal 106 to the antenna 124. Accordingly, the front endmodule 100 can be configured to communicate on the TDD and FDD bandsimultaneously to enable carrier aggregation.

When the front end module 100 implements carrier aggregation includingboth TDD and FDD bands, there can be significant error vector magnitude(EVM) degradation on the FDD band (e.g., path C). EVM can be used as ameasure of the accuracy of transmitted signals. In an example of carrieraggregation, in order to transmit using TDD, the switch 122 may switchback and forth between paths A and B. This switching between the TDDreceive and transmit bands can interfere with signals transmitted on theFDD band (e.g., path C), for example, by briefly connecting the antenna,and thus path C, to ground. The interference on the FDD band will beexplained further below.

Aspects of this disclosure relate to systems and techniques which can beused to suppress or reduce the EVM degradation on the FDD band caused byswitching on the connected TDD bands.

FIG. 6 is an example block diagram of a control system 200 for the frontend module 100 of FIG. 5 in accordance with aspects of this disclosure.As shown in FIG. 6, the switch 122 can include a first switch 212, asecond switch 214, and a third switch 216 respectively connected onpaths A, B, and C. Each of the switches 212-216 is configured toselectively connect the antenna 124 to the corresponding path (e.g.,path A, B, or C) or ground. In the illustrated embodiment, each switchmay comprise a pair of independently controllable single pole singlethrow (SPST) switches. For example, the first switch 212 includes afirst sub-switch 212 a configured to selective connect or disconnect theantenna 124 to the TDD transmit band terminal 102 and a secondsub-switch 212 b configured to selective connect or disconnect the TDDtransmit band terminal 102 to ground. The first sub-switch 212 a mayalso be referred to as a series switch since the first sub-switch 212 acan selectively connect the TDD transmit band terminal 102 to theantenna 124 in series, while the second sub-switch 212 b may also bereferred to as a shunt switch since the second sub-switch 212 b canselectively shunt the TDD transmit band terminal 102 to ground.

The control system 200 system includes a hybrid delay control block 202and a non-delay control block 204. As shown in FIG. 6, the hybrid delaycontrol block 202 is configured to control operation of the first andsecond switches 212 and 214 while the non-delay control block 204 isconfigured to control the third switch 216. During carrier aggregation,the FDD band and the TDD band may operate at the same time. Accordingly,the switch 122 may simultaneously connect the antenna 124 to both theFDD band terminal 110 and one of the TDD transmit and receive bandterminals 102 and 106.

EVM degradation in the FDD band receive path (e.g., path C) may occurwhen switching between the TDD band transmit path (path A) and receivepath (path B). For example, the dynamic on-resistance variation of thethird switch 216 on the FDD band path (path C) during the switchingduration of changing the states of the first and second switches 212 and214. The EVM degradation is caused by simultaneous switching of thefirst and second switches 212 and 214 without delaying the gate controlvoltages of the second sub-switches 212 b and 214 b that shunt the TDDpaths to ground. For example, if one or more of the second sub-switches212 b and 214 b is coupled to ground while the corresponding firstsub-switches 212 a and 214 a remains connected to the antenna 124, theantenna 124 will also be connected to ground. During carrieraggregation, this results in the FDD band path (path C) being shunted toground, which negatively affects EVM of the FDD band.

A delay on connecting the second sub-switches 212 b and 214 b to groundafter disconnecting the corresponding first sub-switches 212 a and 214 acan reduce or prevent the antenna 124 and FDD band from being shunted toground during communication over the FDD band.

The first, second, and third switches 212-216 may be designed to have arelatively large size and high number of stacks to meet stringentperformance requirements for the transmit paths (e.g., paths B and C)such as minimum loss and high power-handling capabilities.

FIG. 7 illustrates example control signals 300 provided to the first andsecond switches 212 and 214. In particular, FIG. 7 illustrates anembodiment in which there is no delay between the switch control signalsprovided to the first and second switches 212 and 214. Referring toFIGS. 6 and 7, the first sub-switch 212 a receives a first seriescontrol signal Ctrl_ser1 and the second sub-switch 212 b receives afirst shunt control signal Ctrl_shn1. Similarly, the second sub-switch212 a receives a second series control signal Ctrl_ser2 and the secondsub-switch 212 b receives a second shunt control signal Ctrl_shn2. Usingthe combination of control signals illustrated in FIG. 7, the shuntsignals Ctrl_shn1 and Ctrl_shn2 have an off value when the correspondingseries signals Ctrl_ser1 and Ctrl_ser2 have an on value, and vice-versa.In addition, the control signals are further configured to connect theantenna to one of the TDD transmit band terminal 102 and the TDD receiveband terminal 106 at a time.

As discussed above, this “instantaneous” switching between series andshunt connections at the first and second switches 212 and 214 mayresult in EVM degradation on the FDD band path (path C). One way inwhich this EVM degradation can be addressed is to add a delay betweenthe switching of the series and shunt sub-switches 212 a, 212 b, 214 a,and 214 for each of the first and second switches. FIG. 8 illustratesexample control signals 400 provided to the first and second switches212 and 214 including a delay in accordance with aspects of thisdisclosure.

The dynamic on-resistance variation in the FDD receive path (path C)when TDD band transmit and receive paths (paths A and B) switch statescan be suppressed by turning off the gate control signals of the secondsub-switches 212 b and 214 b before turning on the series sub-switches212 a and 214 a for the TDD transmit and receive paths (paths A and B).As shown in FIG. 8, there is a gap 402 between the transitions in thecontrol signals Ctrl_ser1, Ctrl_shn1, Ctrl_ser2, and Ctrl_shn2. Inparticular, the gap 402 ensures that the FDD path (path C) is fullydisconnected from the TDD transmit and receive paths (paths A and B)before the TDD transmit or receive band terminals 102 and 106 areshunted to ground.

In some implementations, the gap 402 can be accomplished by generatingthe gate control signals of the series (Ctrl_ser1 and Ctrl_ser2) andshunt (Ctrl_shn1 and Ctrl_shn2) switches so as to non-overlap as shownin FIG. 8. The suppressed disturbance on the on-resistance for the FDDpath switch 216 at during the switching of switches 211 and 214 of theTDD transmit and receive paths (paths A and B) results in a significantimprovement of EVM degradation. The increase in the amount ofnon-overlap in these control signals due to the gap 402 also results inan increase the switching delay time between transitioning between theTDD transmit and receive paths (paths A and B), which is anotherimportant specification in 5G system operation. Accordingly, in someimplementations, the amount of non-overlap (e.g., the length of the gap402) is programmable to allow the compromise between the EVM improvementand decrease of the switching delay to be tuned.

In some embodiments, the amount of the delay (e.g., the length of thegap 402) can be programmed using a hybrid approach combining digital andanalog RC circuitry. FIG. 9 is a block diagram of an exampleprogrammable RC delay circuit 500 which may be included as a part of thehybrid delay control block 202 of FIG. 6 in accordance with aspects ofthis disclosure. The RF delay circuit 500 is configured to receive aplurality of delay control signals Control_in and set the amount delaybetween switching of the control signals Ctrl_ser1, Ctrl_shn1,Ctrl_ser2, and Ctrl_shn2 by providing a plurality of output delaycontrol signals Control_out. The programmable RC delay circuit 500 mayinclude of digital and RC delay circuitry configured to adjust theamount of the delay between transitions in the control signalsCtrl_ser1, Ctrl_shn1, Ctrl_ser2, and Ctrl_shn2.

CONCLUSION

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Likewise, the word “connected”, as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, that word coversall of the following interpretations of the word: any of the items inthe list, all of the items in the list, and any combination of the itemsin the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “can,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A wireless front end system comprising: time-division duplexing transmit and receive terminals, a frequency division duplexing terminal, and an antenna terminal; a first switch configured to selectively connect the time-division duplexing transmit terminal to either a first node or the antenna based on a first control signal, a second switch configured to selectively connect the time-division duplexing receive terminal to either a second node or the antenna based on a second control signal, and a third switch configured to connect the frequency division duplexing terminal to the antenna based on a third control signal; and a controller configured to generate the first, second, and third control signals, and to provide: i) a first delay between switching connection of the time-division duplexing transmit terminal from the antenna to the first node, and ii) a second delay between switching connection of the time-division duplexing receive terminal from the antenna to the second node.
 2. The front end system of claim 1 wherein the first node and the second node are ground nodes.
 3. The front end system of claim 1 wherein the first switch includes a first serial sub-switch configured to selectively connect the time-division duplexing transmit terminal to the antenna and a first shunt sub-switch configured to selectively connect the time-division duplexing transmit terminal to the first node, and the second switch includes a second serial sub-switch configured to selectively connect the time-division duplexing receive terminal to the antenna and a second shunt sub-switch configured to selectively connect the time-division duplexing receive terminal to the second node.
 4. The front end system of claim 3 wherein the first control signal includes a first serial control signal configured to control the first serial sub-switch and a first shunt control signal configured to control the first shunt sub-switch, and the second control signal includes a second serial control signal configured to control the second serial sub-switch and a second shunt control signal configured to control the second shunt sub-switch.
 5. The front end system of claim 4 wherein the controller is further configured to provide the first delay between transitioning the first serial control signal to an off value and transitioning the first shunt control signal to an on value, and the controller is further configured to provide the second delay between transitioning the second serial control signal to the off value and transitioning the second shunt control signal to the on value.
 6. The front end system of claim 5 wherein the controller is further configured to provide a third delay between transitioning the first shunt control signal to the off value and transitioning the first serial control signal to the on value, and the controller is further configured to provide a fourth delay between transitioning the second shunt control signal to the off value and transitioning the second serial control signal to the on value.
 7. The front end system of claim 1 wherein the controller is further configured to adjust a length of the first delay and the second delay.
 8. The front end system of claim 1 wherein the controller includes both digital and analog circuitry configured to implement the first delay and the second delay.
 9. The front end system of claim 1 wherein the controller is further configured to switch between connecting the time-division duplexing transmit terminal and the time-division duplexing receive terminal to the antenna while the frequency division duplexing terminal remains connected to the antenna.
 10. A mobile device comprising: an antenna configured to transmit radio frequency signals to a base station; a time-division duplexing power amplifier, a time-division duplexing low noise amplifier, and a frequency division duplexing terminal; and a front end system coupled to the antenna, the time-division duplexing power amplifier, the time-division duplexing low noise amplifier, and the frequency division duplexing terminal, the front end system including a first switch configured to selectively connect the time-division duplexing power amplifier to either a first node or the antenna based on a first control signal, a second switch configured to selectively connect the time-division duplexing low noise amplifier to either a second node or the antenna based on a second control signal, a third switch configured to connect the frequency division duplexing terminal to the antenna based on a third control signal, and a controller configured to generate the first, second, and third control signals, to provide: i) a first delay between switching connection of the time-division duplexing power amplifier from the antenna to the first node, and ii) a second delay between switching connection of the time-division duplexing low noise amplifier from the antenna to the second node.
 11. The mobile device of claim 10 wherein the first node and the second node are ground nodes.
 12. The mobile device of claim 10 wherein the first switch includes a first serial sub-switch configured to selectively connect the time-division duplexing power amplifier to the antenna and a first shunt sub-switch configured to selectively connect the time-division duplexing power amplifier to the first node, and the second switch includes a second serial sub-switch configured to selectively connect the time-division duplexing low noise amplifier to the antenna and a second shunt sub-switch configured to selectively connect the time-division duplexing low noise amplifier to the second node.
 13. The mobile device of claim 12 wherein the first control signal includes a first serial control signal configured to control the first serial sub-switch and a first shunt control signal configured to control the first shunt sub-switch, and the second control signal includes a second serial control signal configured to control the second serial sub-switch and a second shunt control signal configured to control the second shunt sub-switch.
 14. The mobile device of claim 13 wherein the controller is further configured to provide the first delay between transitioning the first serial control signal to an off value and transitioning the first shunt control signal to an on value, and the controller is further configured to provide the second delay between transitioning the second serial control signal to the off value and transitioning the second shunt control signal to the on value.
 15. The mobile device of claim 14 wherein the controller is further configured to provide a third delay between transitioning the first shunt control signal to the off value and transitioning the first serial control signal to the on value, and the controller is further configured to provide a fourth delay between transitioning the second shunt control signal to the off value and transitioning the second serial control signal to the on value.
 16. The mobile device of claim 10 wherein the controller is further configured to adjust the length of the first delay and the second delay.
 17. The mobile device of claim 10 wherein the controller includes both digital and analog circuitry configured to implement the first delay and the second delay.
 18. The mobile device of claim 10 wherein the controller is further configured to switch between connecting the time-division duplexing power amplifier and the time-division duplexing low noise amplifier to the antenna while the frequency division duplexing terminal remains connected to the antenna.
 19. A method of operating a radio frequency device, comprising: coupling, via a first switch, a time-division duplexing transmit terminal to either a first node or an antenna based on a first control signal; coupling, via a second switch, a time-division duplexing receive terminal to either a second node or the antenna based on a second control signal; coupling, via a third switch, a frequency division duplexing terminal to the antenna based on a third control signal; providing a first delay between switching connection of the time-division duplexing transmit terminal from the antenna to the first node; and providing a second delay between switching connection of the time-division duplexing receiver terminal from the antenna to the second node.
 20. The method of claim 19 further comprising adjusting a length of the first delay and the second delay.
 21. The method of claim 19 further comprising: selectively coupling, via a first serial sub-switch, the time-division duplexing transmit terminal to the antenna; selectively coupling, via a first shunt sub-switch, the time-division duplexing transmit terminal to the first node; selectively coupling, via a second serial sub-switch, the time-division duplexing receive terminal to the antenna; and selectively coupling, a second shunt sub-switch, the time-division duplexing receive terminal to the second node.
 22. The method of claim 21 further comprising: generating a first serial control signal to control the first serial sub-switch; generating a first shunt control signal to control the first shunt sub-switch; generating a second serial control signal to control the second serial sub-switch; and generating a second shunt control signal to control the second shunt sub-switch. 